Precast monolithic structures are increasingly applied in construction. Such a structure has a performance somewhere between that of a pure precast structure and that of a cast-in-place structure. A precast concrete frame structure is one of the most common prefabricated structural systems. The post-pouring joint is important for controlling the seismic performance of the entire precast monolithic frame structure. This paper investigated the joints of a precast prestressed concrete frame structure. A reversed cyclic loading test was carried out on two precast prestressed concrete beam–column joints that were fabricated with two different concrete strengths in the keyway area. This testing was also performed on a cast-in-place reinforced concrete joint for comparison. The phenomena such as joint crack development, yielding, and ultimate damage were observed, and the seismic performance of the proposed precast prestressed concrete joint was determined. The results showed that the precast prestressed concrete joint and the cast-in-place joint had a similar failure mode. The stiffness, bearing capacity, ductility, and energy dissipation were comparable. The hysteresis curves were full and showed that the joints had good energy dissipation. The presence of prestressing tendons limited the development of cracks in the precast beams. The concrete strength of the keyway area had little effect on the seismic performance of the precast prestressed concrete joints. The precast prestressed concrete joints had a seismic performance that was comparable to the equivalent monolithic system.
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Abstract:Compatibility among substructures is an issue for hybrid simulation. Traditionally, the structure model is regarded as the idealized shear model. The equilibrium and compatibility of the axial and rotational direction at the substructure boundary are neglected. To improve the traditional boundary technique, this paper presents a novel substructure hybrid simulation boundary technique based on beam/column inflection points, which can effectively avoid the complex operation for realizing the bending moment at the boundary by using the features of the inflection point where the bending moment need not be simulated in the physical substructure. An axial displacement prediction technique and the equivalent force control method are used to realize the proposed method. The numerical simulation test scheme for the different boundary techniques was designed to consider three factors: (i) the different structural layers; (ii) the line stiffness ratio of the beam to column; and (iii) the peak acceleration. The simulation results for a variety of numerical tests show that the proposed technique shows better performance than the traditional technique, demonstrating its potential in improving HS test accuracy. Finally, the accuracy and feasibility of the proposed boundary technique is verified experimentally through the substructure hybrid simulation tests of a six-story steel frame model.
The cable-stayed bridge with diamond-shaped pylons is one of the most popular bridges because of its obvious advantages such as aesthetical appearance and smaller foundation. However, the diamond-shaped pylons have both inward and outward inclinations, which may result in complicated seismic behavior when subjected to lateral earthquake excitations. To end this, the finite element model of a cable-stayed bridge with diamond concrete pylon is developed firstly. Four limit states and corresponding damage index are defined for each critical section. Finally, the lateral seismic fragility of the components and system of CSB was carried out. Based on the result of probabilistic estimation of lateral seismic responses, the order of the damage probability in all four damage states for each component of bridge is given. The fragility curves of bridge system on the lower bound and upper bound are studied. Moreover, the system fragility of the entire bridge is compared with that of each component.
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